[Milsurplus] RT-68/GRC - the continuing saga

[WA5CAB at cs.com]

Jim,

Your analogies are essentially correct.  The wide band receiver will hear the 
narrow band transmitter but the audio output level will be as though you were 
whispering into the microphone.  The narrow band receiver should hear the 
wide band transmitter OK if you do whisper, although the system noise will be 
10X, all other things being equal.

On the issue of whether there is a problem with the microphone or with the 
transmitter, you could test the mic on another known working transmitter.  But 
you can also take advantage of a feature of the RT-68 that does not use the 
mic.  The RT-68 can transmit a Ring tone.  If you rotate the dial light switch 
knob fully CCW against the spring return, it should key the transmitter and 
modulate it with a fixed 1600 cps tone at fairly high level.

In a message dated 1/31/2007 12:01:57 PM Central Standard Time, 
Jim.Falls at conservation.ca.gov writes: 
> Regarding MY receive issue: let's see if I have this analogy correct. The 
> '68 has a "catcher's mitt" 25 kHz wide, so when you toss a 2.5 kHz signal into 
> it, it hardly registers (bowling ball versus marshmallow)? This would be 
> equivalent of only getting 10% of the expected incoming signal, right? 
> 
> PS#1: I heard another 6m fellow the other night briefly and he was faint and 
> nearly unintelligible in the '68 (1/2 mile range, unknown power output). I 
> had the little ricebox on as a monitor so I could make out what he was saying.
> 
> Regarding THEIR receive issue, their "mitts" are only 2.5 kHz wide, so 90% 
> of my "diluted" 25 kHz signal blows on by and they hear nothing because their 
> rigs are catching only 10%............? 
> 
> PS#2: I can hear myself (ragged audio - tired element?) on the monitor 
> during TX w/the '68 and get feedback during TX w/the monitor rig unless I turn the 
> AF gain down on the '68 (I have it wide open on receive w/a hi-Z speaker).
> 

Robert Downs - Houston
<http://www.wa5cab.com> (Web Store)
MVPA 9480
<wa5cab at cs.com> (Primary email)
<wa5cab at houston.rr.com> (Backup email)
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